(1) Field of the Invention
The invention relates to a data processing system. More specifically, the invention relates to integration of hub and function endpoints on a single chip USB microcontroller within a Universal Serial Bus (USB) topology.
(2) Related Art
The Universal Serial Bus (USB) is a high-speed serial bus following a protocol defined in Universal Serial Bus Specification, Version 1.0 (USB Spec). Modification of this specification can be expected from time to time. The USB provides a standardized approach for peripheral interconnection with a host computer. The USB is set up in a tiered topology with a host on the top tier and USB hubs and functions on subsequent tiers. Each USB device, whether it be a hub or a function, has associated therewith a serial interface engine (SIE) which provides an interface between a backend interface and the transceiver which transmits or receives signals across the serial line. The backend interface manages the data transacted over the USB line.
The USB Spec defines a compound device to be a single physical device that combines one or more functions with a hub in a single package. One possible compound device is created using system level integration having functions implemented on the same board as the hub and always attached to the hub. This is a multi-chip solution including one hub chip and one or more function chips.
In view of the foregoing, it would be desirable to be able to produce a compound device having both hub and function endpoints on a single chip.